Seattleâ€™s biggest toxic mess is going to take more cleanup than previously thought, federal officials said Tuesday in releasing their plan for the Duwamish River Superfund site. But when the cleanup is finished, people will still be warned against eating seafood from the river, officials acknowledged.

The U.S. Environmental Protection Agencyâ€™s final cleanup plan boosts by one-fifth the amount of river bottom to be dredged up and hauled away. In a draft plan released last year, EPA said it would require 84 acres of contaminated river bottom to be removed, while the final plan released Tuesday would expand that to 105 acres. The cost for the remaining work increases from $305 million to $342 million.